Hiller YH-32 Hornet
1950 experimental helicopter model by Hiller
The Hiller YH-32 Hornet (company designation HJ-1) was an American ultralight helicopter built by Hiller Aircraft in the early 1950s. It was a small and unique design: it was powered by two Hiller 8RJ2B ramjet engines mounted on the rotor blade tips, which weighed 13 lb (5.9 kg) each and delivered an equivalent of 45 hp (34 kW) for a total of 90 hp (67 kW). Versions of the HJ-1 Hornet were built for the United States Army and the United States Navy in the early 1950s.
The Hiller Museum identifies the YH-32A, named the Sally Rand, as the first helicopter gunship.
The Hiller HOE-1 became the first production ramjet helicopter, and the Army and Navy flew a small number of these aircraft for a short time to test and evaluate the technology.
Design and development
The Hiller HJ-1 Hornet was an early attempt to build a jet-powered helicopter using ramjets, with work beginning in 1948. Before that there had been experiments with the XH-26 Jet Jeep tip rotor pulse jets.The HJ-1 ramjet tipped rotor propels the rotor and the aircraft. Unlike a conventional helicopter, this mechanically simple design avoids the need for a tail rotor.
Unfortunately, the tip speeds on helicopter rotor blades are subsonic, and ramjets are inefficient at subsonic speeds due to low compression ratio of the inlets. Therefore, the Hornet suffered from high fuel consumption and poor range.
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